push buttons interfacing

[csshah]

HI
I am using CCS PCH 3.219 with microchip 80 pin tqfp PIC 18F8720 board. I want to interface 3 pushbuttons with pic out of which one button is inbuilt in the board at b0(it s working fine) and I tried putting the other 2 buttons at bits b1 and b2 with required resistors but evenif I can see the correct status of pin while button is pressed it is not giving me required functionality i e it stays in the same loop evenif the button is pressed. So if somebody tell me where I m goin wrong or procedure to initialize the port at I/O for port B in CCS PCH

thanks

[Mark]

The first thing you need to due is POST A SMALL BUT COMPLETE PROGRAM that demonstrates the problem. We can tell you where you went wrong if we don't see the code!

[csshah]

#if defined(__PCB__)
#include <16c56.h>
#fuses HS,NOWDT,NOPROTECT
#use delay(clock=20000000)

#elif defined(__PCM__)
#include <16F877.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)

#elif defined(__PCH__)
#include <18F8720.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#endif

#define CURSOR '~'
//#define X 1
//#define Y 2
#include <stdio.h>
#include <LCD.c>
#byte TRISB = 0xFF
#byte PORTB = 0xF81
#bit PB_A = PORTB.0
#bit PB_B = PORTB.1
#bit PB_C = PORTB.2



void main() {

int i,j,X=1,Y=1,current,page=1;
lcd_init();
set_tris_b(0xFF);

for(i=0;PB_B==1;i++) <--the button is low and goes high when pushed
{
delay_ms(6);
lcd_putc("\f ** TEXT1 **\n");
lcd_putc(" TEXT2");
delay_ms(800);
lcd_putc('\f');
delay_ms(800);
}
lcd_putc(" TEXT3\n");
lcd_putc(" TEXT4");
delay_ms(2000);
lcd_putc('\f');

evenif I press the button it doesnt go out of for loop. I also tried all the combinations of conditions and using while loop instead of for.

[fuzzy]

HI

I can't understand why you are using a FOR or While instruction to interface a pushbutton? I normally use an IF and usually i use a debouncing system to avoid error in pushing or multiple switching.

[csshah]

I am still not getting buttons working
here I am checking the button status inside the loop because I want to display same text till the button is pressed. I think I am making mistake in initializing ports. when i use the push button(b0) given on microchip 80 pin tqfp pic18f8720 demo board everything works fine but when i connect external push buttons to some other port pins, it s not working and givin me pulses while checking using CRO.

Please reply ....

thanks

[csshah]

I am still not getting buttons working
here I am checking the button status inside the loop because I want to display same text till the button is pressed. I think I am making mistake in initializing ports. when i use the push button(b0) given on microchip 80 pin tqfp pic18f8720 demo board everything works fine but when i connect external push buttons to some other port pins, it s not working and givin me pulses while checking using CRO.

Please reply ....

thanks

[PCM programmer]

[csshah]

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=84&useSecondary=true&device=en010058&ds=on&uguide=on&dnotes=on&errt=on&mig=on&tut=on&refm=on&broc=on
The only difference in the buttons is the board button is always high and go to low when pushed while the buttons I'm using are opposite to that.

thanks

[Humberto]

Hi csshah,

Your code don't reflect what you expect.

If you want to read a pushbutton connected to an input, the code would look like this:

[PCM programmer]

I looked at the schematic. On that board, pins RB1 and RB2 are used
for RTS and CTS on the serial port. I wouldn't use those pins for
your experiments. Use pins RB3 and RB4 instead. They don't have
any other circuits connected to them.

That board has got LEDs on Port D. So, here's a simple program
that will turn on a LED when you press the switch.

You need to connector your switch (with the pull-up resistor) to Pin B3.
Then compile the following program and try it.

[csshah]

[csshah]

in the above posted code i used RB3 and RB4 but when i run the code, without pressing any button it shows me the output

text1
text2H

H is blinking

thanks

[PCM programmer]

I don't know. You didn't run my test program, so I guess somebody
else will help you.

[guest]

I think you just need modifiy one line in your code:

for(i=0;PB_B==0;i++)
{
delay_ms(6);
lcd_putc("\f ** TEXT1 **\n");
lcd_putc(" TEXT2");
delay_ms(800);
lcd_putc('\f');
delay_ms(800);
}

PB_B stays high by your initialization and goes to low when the button is pressed.

[csshah]

hey thanks for the program. i tried ur program and it s working but when i try to display text using same logic whether the key is pressed or not. evenif i dont press key it shows me text inside the pressed key if loop.

[#include <18F8720.H>
#fuses HS, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock = 20000000)

#include <stdio.h>
#include <LCD_4bit.c>
setup_adc_ports(NO_ANALOGS);


void main() {

int i,X=1,Y=1,current,page=1,P0SW,premuto;
lcd_init();
//SET_TRIS_B(0xFF);
delay_ms(800);

while(1)
{
delay_ms(800);
lcd_putc("\f text1\n"); //<-- i want to display this text constantly
lcd_putc(" text2");
delay_ms(800);

if(input(PIN_B4))
{
delay_ms(800);
lcd_putc("\f pressed");
delay_ms(800);}


else{
lcd_putc("\f text1\n");
lcd_putc(" text2");
delay_ms(800);
}}

}

]